Rock drill bit guide and mast stabilizer

ABSTRACT

A rock drill bit guide comprising a cylindrical tubular element attached to the lower end of a drill mast and aligned with the central longitudinal axis of the drill string. The guide serves to pilot a rock drill bit during collaring of the drill hole. The bit guide also may be forced to penetrate the earth formation being drilled to act as a stabilizer or anchor for the drill mast.

United States Patent 1191 I m1 3,730,285

[56] References Cited Anderson et al; [451 May 1, 1973 [54] ROCK DRILL BIT GUIDE AND MAST 1,774,884 9/1930 Hansen 175/171 STABILIZER 881,280 3/1908 Andersen ...175/2ll X 1,243,580 10/1917 Besancon ...l75/209 X [75] Inventors: Floyd R. Anderson, 2200 Maine St., 541,256 6/1895 Willard ..l75/203 X Quincy, [IL 230 Donald 2,838,282 6/1958 Colquitt ..l75/2ll X 3,280,925 10/1966 Becker et al.... ..175/1 35 X Lakewood Colo 3,390,730 7/1968 Techy et al 75/17! [73] Assignee: Gardner-Denver Company, Quincy,

[IL 1 Primary Examiner-David H. Brown 1 i A t h I M l. Filed: Oct- 1971 r orney Mic ae E artm et a [21] Appl.No.: 187,703 ABSTRACT A rock drill bit guide comprising a cylindrical tubular [52] U s 175/220 175/122 175/209 element attached to the lower end of a drill mast and aligned with the central longitudinal axis of the drill [51] Int. Cl. ..E2lb 15/00, E2lc 11/00 String The guide serves to pilot a rock drill bit during of Search l i g of the hole. The bit guide also y be 175/171 209 2l1 220 forced to penetrate the earth formation being drilled to act as a stabilizer or anchor for the drill mast.

3991!??? D win E'F UNITED STATES PATENTS u 3,072,203 H1963 Bcndixen ..l75/220X BACKGROUND or THE INVENTION In the art of earth drilling it is known to provide drill rod guides or centralizers mounted. near the distal end of the drill mast or feed support for guiding and supporting the elongated drill string to maintain a proper directional attitude of the drill bit. However, in order to provide clearance for the drill bit, which is usually somewhat larger in diameter than the drill rods, conventional centralizers or drill rod guides cannot support the drill string at a position which is contiguous with or immediately adjacent the work surface.

In percussion drilling it is customary to use bits having wedge shaped hard metal inserts arranged in various forms such as a cross or X. A longstanding problem in using such bits has been one of starting or collaring a drill hole in true alignment with the longitudinal central axis of the drill string. In particular when engaged with a rough or uneven work surface or when drilling into a surface not at right angles to the drill string axis most types of percussion rock drill bits have a tendency to deflect the drill rod or extension drill string out of alignment with its normal longitudinal axis upon collaring or starting a drill hole. This problem is particularly acute with wedge insert type bits but is also present with the use of button insert type bits. Lateral excursion of the bit with respect to the drill rod longitudinal axis places the drill rod under a severe bending load as well as developing a drill hole having an undesired directional attitude.

Heretofore in the art of rock drilling, particularly in hard rock formations, the hole collaring process has been carried out at substantially reduced power settings of the drill motor in order to start the hole reasonably true and until a sufficient hole depth is achieved to provide for the side walls of the hole to act as a guide for the drill bit. This process is not only time consuming but has been only partially satisfactory in producing a properly aligned drill hole. Moreover, known auxiliary devices such as conventional drill rod centralizers have proven to be inadequate as a means for guiding the bit.

SUMMARY OF THE INVENTION The present invention provides means for guiding a rock drill bit and associated drill string to prevent lateral deflection and bending of the extension drill rods. The present invention also provides for accurate drill hole location with respect to the central longitu dinal axis ofa drill string and bit by providing means for closely piloting or guiding the bit proper upon starting or collaring a drill hole. More accurate drill hole alignment as well as the performance of collaring operations at high energy input rates are made possible with the present invention, particularly when drilling holes into surfaces which are not perpendicular to the longitudinal axis of the drill string.

The present invention further provides means for steadying a drill feed support or mast to increase the stability of the feed support and the drilling rig while drilling a hole and to substantially prevent movement of the drill rig proper during the drilling process. The

drill bit guide and mast stabilizer according to the present invention is operable to substantially steady a drill feed support when drilling in hard rock as well as in moderately soft and easily penetrable formations.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevation of a rock drill rig including the bit guide and mast stabilizer of the present invention. l

FIG. 2 is a detail view partly in section of the bit guide and mast stabilizer of the present invention.

FIG. 3 is a section taken along the line 3-3 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, the present invention is shown in use on a mobile rock drill rig generally designated by the numeral 10. The rock drill rig 10 is characterized by a crawler type undercarriage 12 upon which is mounted a mast support 14. The mast support 14 is pivotally connected to the undercarriage 12 at 16 and is positioned about the pivot 16 by a pair of side by side pressure fluid cylinder actuators 18, one shown in FIG. 1. The drill rig 10 also includes an elongated mast or drill feed support 20 which is mounted on the mast support 14 and is movable therealong. As shown in FIG. 3 the mast 20 includes a pair of spaced apart longitudinal rails 22 which are slidable in grooves formed by portions 26 on the mast support 14. Power means comprising a double acting pressure fluid cylinder 28 is suitably mounted on the mast support and has its piston rod 30 attached to a bracket 32 mounted on the mast 20. Through a source of pressure fluid and suitable control system, not shown, thecylinder 28 may be actuated to raise the mast or conversely exert a downward bias or pulldown force on the mast.

The drill rig 10 also includes a drill motor 34 mounted on the mast 20 and connected to suitable feeding mechanism, not shown, for feeding the drill motor reciprocably along the mast. The drill motor 34 is connected to an extension drill string 36 made up of a plurality of elongated rods or pipes 37 coupled end to end. The drill motor 34 is operable in a well known way to rotate the drill string 36 about a central longitudinal axis 38 and to deliver impact blows through the drill string to a rock penetrating bit 40 attached to the lower end of the drill string. The bit 40 is of a type known in the art of percussion rock drilling and is characterized by a plurality of hard metal wedge shaped inserts 42 arranged in the form of a cross and supported by bit wings 44. Suitable grooves 46 formed between the bit wings allow for the upward conveyance of rock cuttings from a drill hole with the aid of a suitable flushing medium in a manner well known. a

As shown in FIG. 2, the bit 40 is surrounded by and engageable with the inner wall 46 ofa cylindrical tubular element 48 attached to the lower end of the mast 20. The diameter of the inner wall 46 is slightly larger than the diameter of the bit 40 formed by the radial extremities of the wings 44 to allow free passage of the bit through the tubular element 48. The element 48 comprises means for guiding the bit 40, particularly upon starting or collaring a drill hole, to assure that the drill hole is started in a direction substantially coincident with the longitudinal axis 38 of the drill string. The guide element 48 has a distal end portion having a sloping surface 50 forming an edge 51 to facilitate penetration of the earth formation to be drilled. The guide element 48 is detachably secured to a plate 52 by means of suitable fasteners 54. A pilot flange 56 is formed on the guide element and fits into a cooperating pilot bore 58 on the plate 52. The plate 52 is supported by legs 60 attached to a transverse member 62 at the lower end of I the mast 20. The member 62 also supports a combination drill rod centralizer and breakout device 64 for uncoupling the drill rods 37, one from another.

The guide element 48 not only provides for assuring that the bit collars a drill hole in a desired directional attitude but in accordance with the present invention the guide element 48 also is operable to stabilize or steady the mast 20 and, accordingly, the drill rig also. As shown in FIG. 1, the guide element 48 is substantially embedded in an earth formation 65 and thereby serves to stabilize and steady the mast 20. Particularly when drilling through soft or loose overburden, the pulldown cylinder 28 may be actuated to exert a downward force on the mast to force the guide element 48 to penetrate the earth formation to the depth shown in FIG. 1.

In very hard rock the guide element is forcibly engaged with a rock surface 66, as represented in FIG. 2 by the solid lines, prior to the hole collaring operation, by exerting a downward bias on the mast through the pulldown cylinder 28. When the bit 40 is impacted and rotated to penetrate the rock formation a certain amount of well known overbreak or enlarging of the hole diameter beyond the radial extremities of the bit occurs, particularly in hard rock, as shown by the dotted lines in FIG. 2. The enlarged diameter of the drill hole 68 makes possible the entry therein of at least a portion of the sloping surface 50 of the guide element whereby the guide element operates to stabilize the mast 20 in very hard formations as well as in somewhat soft ones. The relatively thin walled cylindrical form of the bit guide element together with the edge 51 formed by the sloping surface 50 facilitates the ease with which the guide may be forced to penetrate an earth formation. The guide element may be suitably manufactured of cast ductile iron.

By providing a bit guide such as the guide element 48 any tendency for the bit 40 to undergo lateral excursion with respect to the axis 38 is prevented during the hole collaring operation. Accordingly, there is 'alsoa substantially reduced tendency for the drill string to be subjected to any bending loads due to drill hole misalignment and the useful life of the drill string components as well as the centralizer 64 are enhanced.

What is claimed is:

1. In a drill rig:

a support;

an elongated drill feed support mounted for longitudinal movement on said support;

power means attached to said support and said feed support for urging said feed support to move longitudinally with respect to said support;

a drill motor mounted on said feed support for reciprocal movement along said feed support;

a drill string having one end connected to said drill motor to be rotated by said drill motor about a longitudinal axis;

a rock penetrating bit attached to the opposite end of said drill string and rotatable with said drill string;

and, means mounted on said feed support surrounding and engageable with said bit for guiding said bit to substantially prevent lateral excursion of said bit with respect to said longitudinal axis upon starting a drill hole, said means including a distal end portion for forcibly engaging a rock formation surface to be penetrated by said bit to stabilize said feed support in response to the exertion of a longitudinal bias force on said feed support by said power means.

2. The invention set forth in claim 1 wherein:

said means for guiding said bit comprises a substantially cylindrical tubular element having a cylindrical inner wall surface surrounding and engageable with said bit.

3. The invention set forth in claim 2 wherein:

said tubular element includes a distal end portion having a sloping surface forming an edge for penetrating said rock formation to stabilize said feed support against lateral movement with respect to a drill hole. 

1. In a drill rig: a support; an elongated drill feed support mounted for longitudinal movement on said support; power means attached to said support and said feed support for urging said feed support to move longitudinally with respect to said support; a drill motor mounted on said feed support for reciprocal movement along said feed support; a drill string having one end connected to said drill motor to be rotated by said drill motor about a longitudinal axis; a rock penetrating bit attached to the opposite end of said drill string and rotatable with said drill string; and, means mounted on said feed support surrounding and engageable with said bit for guiding said bit to substantially prevent lateral excursion of said bit with respect to said longitudinal axis upon starting a drill hole, said means including a distal end portion for forcibly engaging a rock formation surface to be penetrated by said bit to stabilize said feed support in response to the exertion of a longitudinal bias force on said feed support by said power means.
 2. The invention set forth in claim 1 wherein: said means for guiding said bit comprises a substantially cylindrical tubular element having a cylindrical inner wall surface surrounding and engageable with said bit.
 3. The invention set forth in claim 2 wherein: said tubular element includes a distal end portion having a sloping surface forming an edge for penetrating said rock formation to stabilize said feed support against lateral movement with respect to a drill hole. 